How do you use a multiple leaf texture file on a sapling curve tree?
Multiple objects can use different parts of the same material using UV mapping. In this example, The original UVs of the image plane are cut automatically when using the Knife tool. Split the edges and separate the loose parts to create multiple objects. Note the single material used.

That same material can also use the same UVs for applying alpha, normals etc...

Note: the "Import Image as Plane" is an Addon.